Phase change inks (sometimes referred to as “solid inks” and “hot melt inks”) have been used in various liquid deposition techniques. Phase change inks often contain a “phase-change agent” that enables the ink to exist in a solid phase at ambient temperatures, but also exist in the liquid phase at the elevated operating temperature of an ink jet printing device. At the deposit operating temperature, droplets of liquid ink are ejected from the printing device and, as the ink is jetted towards or contacts the surface of the recording substrate, either directly or via an intermediate heated transfer belt or drum, the ink rapidly solidifies onto the substrate to form a predetermined pattern of solidified ink marks. Phase change inks have also been used in other printing technologies, such as gravure printing, as disclosed in, for example, U.S. Pat. No. 5,496,879, the entire disclosure of which is totally incorporated herein by reference. Phase change inks have also been used for applications such as postal marking, industrial marking, and labeling.
Phase change inks are desirable for ink jet printers because they remain in a solid phase at room temperature, which is convenient during shipping and ink handling, enables long term storage, and ease of use. In addition, the problems associated with nozzle clogging as a result of ink evaporation with liquid ink jet inks are largely eliminated, thereby greatly improving the reliability of the ink jet printing. Further, in phase change ink jet printers wherein the ink droplets are applied directly onto the final recording substrate (for example, paper, transparency material, and the like), the droplets solidify immediately upon contact with the substrate, so that migration of ink along the printing medium is prevented and image quality is improved.
Ink jet printing systems generally are of two types: continuous stream and drop-on-demand, as described in U.S. Pat. No. 6,547,380. The entire disclosures of U.S. Pat. Nos. 5,195,430 and 6,547,380 are totally incorporated herein by reference.
There are at least three types of drop-on-demand ink jet systems. One type of drop-on-demand system is a piezoelectric device that has as its major components an ink filled channel or passageway having a nozzle on one end and a piezoelectric transducer near the other end to produce pressure pulses. Another type of drop-on-demand system is known as acoustic ink printing. Still another type of drop-on-demand system is known as thermal ink jet, or bubble jet, and produces high velocity droplets.
In a typical design of a piezoelectric ink jet device utilizing phase change inks printing directly on a substrate or on an intermediate transfer member, such as the ones described in U.S. Pat. Nos. 5,372,852; 7,063,410; and 7,448,719 the disclosures of which are hereby incorporated by reference in their entireties. At the jet operating temperature, droplets of liquid ink are ejected from the printing device and, when the ink droplets contact the surface of the recording substrate, either directly or via an intermediate heated transfer belt or drum, they rapidly solidify to form a predetermined pattern of solidified ink drops. This approach simplifies the printhead design, and the small movements ensure good droplet registration and allows for printing directly on a substrate or on an intermediate transfer member.
Phase change inks for use in such jet printing systems generally are in the solid phase at, for example, ambient or room temperature, such as about 20° C. to about 25° C., but exist in the liquid phase at the elevated operating temperature of an ink jet printing device. At the jet operating temperature, the ink is molten and droplets of liquid ink are ejected from the printing device. In order to display such properties, known phase change inks generally contain components such as crystalline waxes and other materials that enable sharp and rapid phase transitions from the molten liquid state to the solid state. Many known phase change inks, however, exhibit disadvantages such as poor adhesion to coated paper substrates, resulting in poor scratch-resistance, poor image robustness, hard and brittle properties, poor ‘paper fold’ performance such as cracking and creasing of the image when the document is folded, and document offset. Further, the nonpolarity of these ink components often leads to compatibility issues with commonly available dyes and pigments, resulting in the need for more expensive or custom-designed colorants to ensure good solubility or dispersibility in the ink carrier and good long-term thermal stability to prevent colorant degradation or colorant migration.
Customers have also created a demand for materials that are bio-renewable or derived at least partly from renewable resources. Energy and environmental policies, increasing and volatile oil prices, and public/political awareness of the rapid depletion of global fossil reserves have created a need to find sustainable monomers derived from bio-renewable materials. By using biorenewable feedstock, manufacturers can reduce their carbon footprint and move to a zero-carbon or even a carbon-neutral footprint.
Accordingly, while known materials and processes are suitable for their intended purposes, there is a need for improved phase change inks. In addition, there is a need for phase change inks that exhibit sharp and rapid phase transitions from the molten liquid state to the solid state. Further, there is a need for phase change inks that exhibit good adhesion to coated paper substrates. Additionally, there is a need for phase change inks that exhibit good scratch-resistance. There is also a need for phase change inks that exhibit good image robustness. In addition, there is a need for phase change inks that exhibit good “paper fold” performance and reduced cracking and creasing of the image when the document is folded. Further, there is a need for phase change inks that exhibit good document offset performance.
Additionally, there is a need for phase change inks that exhibit good compatibility with commonly available colorants. In addition, a need remains for phase change inks that contain at least some materials at least partly derived from renewable resources. Further, a need remains for phase change inks that can be prepared at desirably low cost. There is also a need for phase change inks that contain some biodegradable components. These and other needs and advantages can be achievable with the compositions comprising ester resins, such as Abitol E ester resins of the present disclosure.